Initial stability

Like a flat-bottomed vase, some hull forms are stable to a certain angle of heel, and will return to the level if released. But, like the vase, if pushed too far they go right over. They have only initial stability. The round¬bottomed toy clown who comes up from any angle has more than initial stability – his is ultimate. Beamy flat-bottomed boats have high initial stability, and so do catamarans, but neither type has the ultimate stability of the boat with a deep ballasted keel which will pick herself up even if knocked flat. (The beamy barge-type boat should not be knocked flat, of course, nor should a catamaran. That would be carelessness and poor seamanship.)